Around two hours later at Chelsea and Westminster Hospital, a doctor found she had blood alcohol of 300 milligrams per decilitre, which is almost four times the legal drink and drive limit of 80.

Despite the deep level of inebriation, a misconduct panel looking into the incident says there is no evidence that pupils at the school were aware she was drunk.

The elite prep school hired Mrs Bourne to teach Latin to pupils from Year 6 to 8 and Classics to pupils in Year 5.

She had been due to teach two lessons at 10 am and at 11.20 am she was due to invigilate a double-period of exams.

The misconduct panel looking into her behaviour found that she had turned up to invigilate, but was not in a fit state to have stayed due to her drinking.

The panel found she had attended the school while under the influence of alcohol, and failed to maintain high standards of behaviour by being unable to perform her duties as a result of being under the influence of alcohol.

Mrs Bourne told the panel she had “no desire” to return to the teaching profession after the incident.

The report into her misconduct, which was published on Monday, noted: “No doubt had been cast upon her abilities as a teacher, although the panel was not presented with any character references or testimonials.

They also noted in mitigation that Mrs Bourne “had a number of significant personal difficulties at the relevant time, including family and health issues, and there was some evidence of work-related pressures”.

They went on to add that she made “commendable efforts to address the issues which she has asserted led to her acting as she did”.

Although some aspects of her behaviour could have resulted in a professional banning order, meaning she could never work again as a teacher, the panel recommended the order not be made.

“Having very carefully taken account of the public interest considerations present,the panel considered that the publication of the adverse findings it made would be sufficient to send an appropriate message to the teacher as to the standards of behaviour that were not acceptable,” wrote the report’s chair, Dr Melvyn Kershaw.

“The panel considered this to be a proportionate outcome which struck a fair balance between both the public interest and Mrs Bourne’s interests.”

Alan Meyrick, Chief Executive of the Teaching Regulation Agency agreed with the panel’s decision on behalf of Education Secretary Gavin Williamson. My London